Mining operations require the transport of highly abrasive particulate or slurry streams. The recovery of bitumen from oil sands is becoming increasingly important in the energy industry. Processing oil sand includes transporting and conditioning the oil sand as aqueous slurry over kilometer lengths of pipe up to one meter or more in diameter, at average slurry flow velocities from 2 to 6 m/s. Often, metal pipes such as carbon steel or cast iron pipes are used for the transport of these highly abrasive streams of oil sand slurry. They are expensive, heavy and only provide a temporary solution since they are eventually destroyed. To increase their lifetimes, the metal pipes may be rotated 90 degrees on their axes on a regular schedule to provide new transport surfaces. However, because of the pipe weight, this rotation is difficult and ultimately the entire pipe is worn out and must be replaced.
Use of plastic pipes, pipe liners and pipe coatings has been proposed to reduce these shortcomings. Many of the commonly available materials cannot stand up to such highly-abrasive mining streams and are quickly worn out. For example, high density poly(ethylene) pipes are generally used as liners for sanitary sewer and wastewater pipelines but they rapidly degrade under highly abrasive environments. U.S. Pat. No. 4,042,559 discloses abrasive granule-filled, partially-cured coatings for use in abrasion resistant coated pipes for the transport of mining slurries. U.S. Pat. No. 4,254,165 discloses processes to produce abrasion resistant pipes with 0.04-0.05-inch thick coatings of filled (such as sand) polyolefins, such as low and medium density poly(ethylene). U.S. Pat. No. 4,407,893 discloses a method for coating a metal surface with a composition comprising a polyolefin and an ionomer.
U.S. Patent Application Publications 2009/0107572 and 2009/0107553 describe abrasion resistant ionomer lined steel pipes. U.S. Patent Application Publication 2010/0108173 discloses abrasion resistant polyolefin lined steel pipes. References to other plastic pipe liners and methods for lining a pipe with a polymeric liner can be found in those publications.
U.S. Patent Application Publication 2010/0059132 describes abrasion resistant pipe liners comprising an abrasion resistant inner layer and a second structural layer comprising extrudable polymer materials. The abrasion resistant layer can be formed from a material having elastic rubber-like properties or a greater hardness than the material forming the structural layer, such as ultrahigh molecular weight polyethylene or polyamide.
In some cases, additional materials have been used to adhere polymeric pipe liners to metal pipes. Japanese Patent Application JP2000179752 discloses the use of epoxy primers to adhere ionomer tubes to water service metal pipes. The methods described therein involve either preheating the pipe prior to coating with epoxy or post-coating heating to cure the epoxy. European Patent Application EP 0181233 discloses a method for applying a protective coating to a pipe comprising applying an epoxy coating followed by applying one or more polymeric layers. Heating the pipe to cure the epoxy adds to the complexity and expense to prepare the steel pipe for bonding to the ionomer liner.
U.S. Patent Application Publication 2010/0009086 discloses a rapid-cure epoxy coating system for protecting the exterior of pipes. U.S. patent application Ser. No. 13/313,186 describes a method for bonding ionomer compositions to a metal substrate using an epoxy composition.
Because of the extreme conditions that lined pipes experience during hydroslurry operations, good adhesion of the liner to the metal pipe casing is important. It is also important that the liner have sufficient resistance to wear from the abrasive slurries to protect the pipe. Other useful properties include good chemical resistance, high temperature resistance, and low moisture transmittance. It may be difficult to attain all properties desirable for a pipe liner in a single material. Therefore, multilayer structures with layers comprising different materials may be advantageous for a pipe liner. For example, one surface layer of a multilayer structure may provide good adhesion to the metal substrate and a second surface layer may provide good abrasion resistance.